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MOLECULAR WEIGHT OF ORGANIC BASES         47

The molecular weight of the salt is calculated from the weight
ixj of the platinum, and IV of the salt, according to the formula
(the atomic weight of platinum being 195) :—
Wx 195
w
To determine from this the weight of the base, it is necessary
to deduct from the molecular weight of the salt that of H2PtC)6,                    /-I
and as two molecules of  the  base are contained in the salt,                    * |,
the result is halved.                                                                                     «£ y
Example—07010 grm. of aniline chloroplatinate,                                      ^
(C6H5NH2)2H2PtCle,                                                  'ijji
gave 0*2303 grm. platinum.                                                                           J'J
O7oio_xj95 = 594.2.   M.W. of the salt.                                     t-j
°'2303
594^-_ 409-9 = 9ri ^                                              )f|4
2                                                                 v#
Calculated for C6H7N ; M = 93.                          "                    j/V
:;l*
Preparations                                                *T
General Remarks.—Carefully read through the method.
References to the process are given under each heading. Be
clear as to the objects of the various steps described and the
nature of the materials employed. It cannot be too strongly urged
that in all cases where any doubt exists as to the nature of an
operation, a preliminary trial should be made in a test-tube with a
small quantity of the substance. This is especially necessary in
crystallisation where the quantity and character of the solvent are
unknown. A vast amount of time and material is thereby saved.
A small stock of clean and dry test-tubes (5 x f and smaller sizes)
should always be at hand for this purpose ; also watch-glasses
for microscopic examination of solid substances.
The yield of either the crude or purified product should
always be ascertained, and the purity of the product determined
either by the boiling-point or melting-point. A small rough
balance with celluloid pans, for use on the bench, is indispensable.
Select vessels of a size appropriate to the quantities dealt
with. Never use beakers for boiling or evaporating liquids, but
flasks and basins. Use ordinary, carefully selected,'corks rather